Apparently squats aren't the best thing for building ass- hip thrusts (or bridges) will target the glutes more directly.
A Squat Devotee No More | Bret Contreras
What exactly is the hip thrust and how do I perform it?
While you hip thrust, flex/squeeze the glutes and use them to push the load up. It’s also essential to lock out at the top of the lift. Now, don’t look at the apt/ppt chart below and assume that I’m in anterior pelvic tilt. I’m really in posterior pelvic tilt here, but my glute size might make it appear as if I’m in apt. It’s very important to keep that apt to ppt motion throughout the lift to maximally target the glutes
While hip thrusting, you will go from an initial sitting position (see above photo) in which your lumbar (lower back) is in a slight arch and your pelvis in very slight anterior pelvic tilt, to the top of the lift where you lock your glutes out toward a posterior pelvic tilt motion, which means you’re using the glues to push the pelvis forward (or toward the sky if you’re laying down). The glutes work to keep your pelvis from drifting into anterior pelvic tilt (apt), and also as what’s pushing the load up (and possibly posterior pelvic tilting). Now, while you squat, your lower back keeps an arch (apt), and the glutes can’t fire as hard while you are in an anterior pelvic tilt. Don’t believe me? Arch your back and squeeze your glutes. Now get into a neutral spine position and squeeze the glutes. Huge difference, huh? (Thanks Bret Contreras!)
See how her lower back is arched? This is the squat version of anterior pelvic tilt.
The glutes can’t fire maximally when the pelvis is in apt
Also, the hip thrust is like a bench press, but for the posterior chain. You’re pushing down right on top of the pelvis (with a barbell) and forcing the glutes to pick it up from a horizontal vector. This lift will absolutely elicit the most intense glute burn you have ever felt. Perhaps you’d care to view barbell hip thrusting solely as a bent leg hip extensior/hip hyperextensor lift instead of stressing over pelvic mechanics. When you ascend during the hip thrust, there is movement, and the glutes will fire. Ideally, I’d prefer everyone at least learn and become aware of the different pelvic tilts, but I do undertstand that some people perform the lift best while only thinking of hip extension (and possibly posterior pelvic tilting). Now, while you squat, your lower back keeps an arch (apt), and the glutes can’t fire as hard while you are in an anterior pelvic tilt. Don’t believe me? Arch your back and squeeze your glutes. Now get into a neutral spine position and squeeze the glutes. Huge difference, huh? (Thanks Bret Contreras!)
Do you see how she has a low back arch in the initial stage of the lift (apt)? She is moving her pelvis from an anterior pelvic tilt to a posterior pelvic tilt. It is also important to remember to squeeze the glutes and lock out during each rep
(hope that helps someone)